The main objective of this project is to analyze changes in homotypic cell-to-cell adhesion during the evolution of chemically induced rat hepatocarcinogenesis and to identify the cell surface proteins that are involved in this process. Examination of intercellular homotypic adhesive properties of 14 clones derived from a neonatal Fischer rat liver epithelial cell line (FNRL) showed that the clones differ both in response to dissociation by trypsin treatment and reaggregation rates. Increased adhesion among the clones was associated with an increased proportion of aneuploid cells in the clones. The parent cell line and the clones were unable to grow in soft agarose in the absence or presence of 2 ng/ml of epidermal growth factor (EGF). The rat hepatoma cell line H4-II-E showed negligible capacity to reaggregate after dissociation into single cells and these cells readily formed colonies in soft agarose. Markedly elevated amounts of two acidic glycoproteins (105 cd and 67 kd) wre detected in the "most adhesive" clone when the two-dimensional gel electrophoresis (2D-PAGE) pattern of concanavalin A (Con A)-binding glycoproteins in this clone was compared to that of the "least adhesive clone." 2D-PAGE patterns of plasma membrane glycoproteins isolated by Con A affinity chromatography from normal, preneoplastic and neoplastic livers showed both qualitative and quantitative changes among the samples. Qualitative differences consisted of four new polypeptides appearing in preneoplastic liver versus control liver, four polypeptides lacking in neoplastic liver, and five polypeptides appearing new in neoplastic liver compared with control liver. These findings support the hypothesis that modulation of normal cell surface components, especially glycoproteins involved in cell-to-cell or cell-to-matrix adhesion and communication, may be responsible for some of the biological behavior of cancer cells.